1. Field of the Invention
The invention relates to a method of manufacturing a semiconductor device called an area-array package. The area-array package type semiconductor device, such as a BGA (Ball Grid Array) or a CSP (Chip Size Package), has external terminals each of which is disposed in a single area, and the external terminals are arranged in a grid.
2. Description of the Related Art
A semiconductor device includes a semiconductor chip encapsulated by resin. The semiconductor chip includes integrated circuits on its main surface and a plurality of terminals on its main surface connecting to the integrated circuits. One of such semiconductor devices is an area-array package type semiconductor device. The area-array package type semiconductor device also includes external terminals, each of which connects one of the terminals formed on the semiconductor chip. The external terminals are arranged in a grid.
The methods of manufacturing the area-array package type semiconductor device are introduced in Japanese laid open patent No. 2000-252389, Japanese laid open patent No. 2000-252388 and Japanese laid open patent No. 2000-252390. According to these publications, metal leaf is disposed in a mold, and then, resin material is introduced in the mold with pressure. Since the mold has concavity or convexity arranged in a grid on its surface, the metal leaf is transformed along the concavity or convexity by using pressure applied to the resin material when the resin material is introduced in the mold. The terminals formed on the semiconductor chip is connected to the metal leaf formed on the concavity or convexity by bonding wires. After the resin material is solidified, the semiconductor device is detached from the mold. Since the metal leaf is fixed to the solidified resin, the metal leaf is exposed at the bottom of the semiconductor device. The exposed metal leaf is divided into a plurality of the separated area in a grid by high pressure jet water or laser beam. Each separated area formed of the metal leaf becomes an external terminal base, and an external terminal such as solder ball is formed on each external terminal base.
However, according to the method described above, since the metal leaf exposed from the bottom of the resin material is divided, the resin may also be damaged by the over-cutting. This may cause the semiconductor chip or the bonding wires connected the semiconductor chip to be damaged.